1. Field of the Invention
The present invention relates to a technology of a Round Trip Time (RTT) test to be performed for authenticating an apparatus in a communication system.
2. Description of the Related Art
In a communication system, a technology of a Round Trip Time (RTT) test to be performed for authenticating an apparatus has been known in a system including a plurality of apparatuses connected over a network. In the system, a source that is an apparatus transmitting a content authenticates an apparatus that is a destination of the content and transmits the content to the authenticated apparatus. (Refer to Japanese Unexamined Patent Application Publication No. 2004-295337 and Hitachi, Ltd., Intel Corporation, Matsushita Electric Industrial Co., Ltd., Sony Corporation and Toshiba Corporation, “DTCP Volume 1 supplement F DTCP 1394 Additional Localization D (Informational Version)”, P. 4-9, [online], Jun. 15, 2007, Digital Transmission Licensing Administrator (DTLA), [searched on Dec. 22, 2009], the Internet (http://www.dtcp.com/data/info 20070615 DTCP V1SF 1p 0.pdf)).
According to the technology, when receiving an authentication request from another apparatus, the source checks whether the apparatus having issued the authentication request has already passed an RTT test (including measuring an RTT and determining whether the RTT is within a predetermined period of time or not). If it has passed, the processing moves to the authentication processing. If not, the source performs an RTT test on the apparatus having issued the authentication request. Only if the apparatus passes the RTT test, the processing moves to authentication processing. Thus, the range of transmission of the content from the source can be limited to a local range.
As described above, when the source receives an authentication request from another apparatus, an RTT test may be performed on the apparatus having issued the authentication request. In that case however, because one apparatus may require authentication processing for each channel used for transferring a content for the apparatus configuration or may need independent encoding for each content, authentication requests may be serially issued to the source for a plurality of contents to be received from the source. Then, the following problems may occur.
In other words, when authentication requests are processed in parallel, a plurality of RTT tests are to be performed redundantly on the same apparatus having issued the authentication request because the apparatus has not passed the RTT test. This may induce the failure of the RTT tests because an increased load may be imposed on the apparatus having issued the authentication request.
On the other hand, when authentication requests are processed one by one sequentially, processing on later authentication requests may relatively delay.